diff --git a/app/classes/state/node/YarnInstallState.js b/app/classes/state/node/YarnInstallState.js
new file mode 100644
index 0000000..dfb979b
--- /dev/null
+++ b/app/classes/state/node/YarnInstallState.js
@@ -0,0 +1,43 @@
+const State = require('../State')
+
+class YarnInstallState extends State {
+    #ran_once = false
+
+    static get services() {
+        return [...super.services, 'output']
+    }
+
+    async apply() {
+        const cmd = `cd "${this._config.path}" && yarn install`
+        await this._host.run(cmd)
+        this.#ran_once = true
+    }
+
+    async check() {
+        if ( this._config.force ) return this.#ran_once
+        else {
+            const node_modules = this._host.get_path(`${this._config.path}/node_modules`)
+            await node_modules.classify()
+            return node_modules.is_directory()
+        }
+    }
+
+    async reverse() {
+        const node_modules = this._host.get_path(`${this._config.path}/node_modules`)
+        await node_modules.unlink()
+    }
+
+    failure_message() {
+        return `The Yarn packages at ${this._config.path} need to be installed.`
+    }
+
+    check_message() {
+        return this.failure_message()
+    }
+
+    display() {
+        return `Ensure that the Yarn packages at ${this._config.path} are installed...`
+    }
+}
+
+module.exports = exports = YarnInstallState
diff --git a/app/services/states.service.js b/app/services/states.service.js
index 3168516..766b48f 100644
--- a/app/services/states.service.js
+++ b/app/services/states.service.js
@@ -41,6 +41,8 @@ class StatesService extends Service {
         'service.daemon.reloaded': require('../classes/state/os/ServiceDaemonReloadState'),
 
         'web.download': require('../classes/state/fs/DownloadState'),
+
+        'node.yarn.installed': require('../classes/state/node/YarnInstallState'),
     }
 
     static get services() {
diff --git a/config/routines/example.config.js b/config/routines/example.config.js
index 54c747b..66881ef 100644
--- a/config/routines/example.config.js
+++ b/config/routines/example.config.js
@@ -152,6 +152,13 @@ const example_routine = {
             source: 'https://static.garrettmills.dev/assets/flitter/flitter_f.png',
             path: '/tmp/flitter_f.png',
         },
+        {
+            // State: the packages for the given path are installed via Yarn
+            type: 'node.yarn.installed',
+            host: 'localhost',
+            path: '/home/user/path/to/project',
+            force: true, // default: false
+        },
     ],
 }